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Old 01-24-2008, 12:02 PM
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What to do with BBC 427 Tall Deck?

We found a 427 tall deck motor that powers an old monster of a beer truck (cab over motor style). I've never actually seen a 427 tall deck before, but low and behold this is one!

Anyways I was going to just toss it in a '65 impala project that I was working on, but I'm starting to wonder if it's a better idea to take advantage of the extra block size and give it a healthy stroker kit. Is there any advantage to having a tall deck block to work with? Why was it that the heavy duty/industrial applications used the tall deck?

Just got the brain gears turning.

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Old 01-24-2008, 12:24 PM
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Quote:
Originally Posted by KNanthrup
We found a 427 tall deck motor that powers an old monster of a beer truck (cab over motor style). I've never actually seen a 427 tall deck before, but low and behold this is one!

Anyways I was going to just toss it in a '65 impala project that I was working on, but I'm starting to wonder if it's a better idea to take advantage of the extra block size and give it a healthy stroker kit. Is there any advantage to having a tall deck block to work with? Why was it that the heavy duty/industrial applications used the tall deck?

Just got the brain gears turning.
"Heavy Duty" explains it. Car engines really don't work very hard, their structure is comparatively weak when the needs of trucks, boats or airplanes are looked at. Those type vehicles use the engine at 70 to 90 percent capacity all the time compared to the family auto at maybe 15-20 percent.

The tall block makes an excellent platform for a boat engine. For a race engine it's a bit heavy but offers high strength and space for a stroker and or long rods without the usual compromises to part dimensions in other places, like carving off the big end of rods and their bolts or running pistons with the pins so high they get into the ring lands and result in Mickey Mouse measures to support the rings. In a street rod it offers all the same strength options as when used for a boat or race car with the usual negative of being heavier and larger so handling and space become issues to be dealt with.

You need to inspect old truck engines carefully, they've worked hard and may well have used much of their structural fatigue life. Careful use of dye penetrant and Magna-flux inspection will disclose any crack formation. Measuring the cam and crank bearing bores, pan line and head deck for straightness will expose any twists or sags that have developed from hard use. The amount of bore wear should be carefully measured along with inspection for cracks in the bore walls. These are things that would show the block is or has become tired and shouldn't be used. The crank and rods should also be given a careful inspection for cracking, and proper, or at least salvageable, dimensions.

Bogie
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Old 01-24-2008, 12:40 PM
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Quote:
Originally Posted by oldbogie
"Heavy Duty" explains it. Car engines really don't work very hard, their structure is comparatively weak when the needs of trucks, boats or airplanes are looked at. Those type vehicles use the engine at 70 to 90 percent capacity all the time compared to the family auto at maybe 15-20 percent.

The tall block makes an excellent platform for a boat engine. For a race engine it's a bit heavy but offers high strength and space for a stroker and or long rods without the usual compromises to part dimensions in other places, like carving off the big end of rods and their bolts or running pistons with the pins so high they get into the ring lands and result in Mickey Mouse measures to support the rings. In a street rod it offers all the same strength options as when used for a boat or race car with the usual negative of being heavier and larger so handling and space become issues to be dealt with.

You need to inspect old truck engines carefully, they've worked hard and may well have used much of their structural fatigue life. Careful use of dye penetrant and Magna-flux inspection will disclose any crack formation. Measuring the cam and crank bearing bores, pan line and head deck for straightness will expose any twists or sags that have developed from hard use. The amount of bore wear should be carefully measured along with inspection for cracks in the bore walls. These are things that would show the block is or has become tired and shouldn't be used. The crank and rods should also be given a careful inspection for cracking, and proper, or at least salvageable, dimensions.

Bogie
That's great information, thanks Bogie. So does that just mean that the tall deck is to allow for more structural integrity? So even though a 427 tall deck has the same bore/stroke as a regular 427, are the internals a little different? ie. heavier rods, heavier crank, etc.?

I'll tear it down and see what the internals look like. It does run in the truck as it sits just fine (not that it means anything). My use for it would just be for a street toy, a '65 impala which I would like to have a mild build with good power but im not building it for racing. I guess I'm going for something more unique than a 350/350 setup and I figured the 427 would be cool and even better if I bought a stroker kit for it just for fun. But as I said im just doing some brainstorming right now.

I appreciate the feedback.
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Old 01-24-2008, 12:58 PM
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I' sure you would'nt have any difficulty getting help from one of us emptying the beer truck either! lol
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Old 01-24-2008, 01:03 PM
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Bore it big, stroke it big
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Old 01-24-2008, 01:03 PM
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The 572 is based on the tall deck block.If built right it makes a great street engine as it has tons of low end torque.If you look at the 57 chevy in NEW INTERIORS photo gallery it has a tall deck 427.
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Old 01-24-2008, 01:35 PM
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This is a tall deck 427, that is now a 496.

I got it for 500 bucks and built it right, I couldn't be happier.

The weight difference is about 60 lbs between tall and short decks, replace the intake and water pump with alumium pieces and you have negated the difference already, replace the heads with aluminum and you will be approaching stock 350 weight. Unless you are trying to shave tenths of a second it is not a big deal.

They usually have 4 bolt mains and forged crankshafts, the cranks will work for any 427 or 396 so people will pay good money for them. As long as they aren't too torn up.

If you are going to replace the rods and pistons anyways so why not stroke it? That is another way to lighten the engine...get rid of those 4 piston ring slugs.
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Old 01-24-2008, 01:46 PM
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I am currently building a 427 Tall deck, Everything i learned about it was from this site so make sure if you have ANY questions ask..you will always get an answer. Everything has pretty much been said about the 427 they were built for torque and torque only i think mine stock was 220 hp and 400 tq. I have installed...Edelbrock carb, summit cam, headers, .040 over, 750 cfm edelbrock carb, roller rockers, alumnium heads, all new bearings. I had the block magnafluxed and pressure tested for cracks and all was good. Like you i also wanted something differnent then the usualll 350, but mine is going in an 84 scottsdale so i dont have to worry about room and all i want is tq. I had v23 test on a program approx hp and tq for it and i was around 520hp and 540tq , 450 tq at 2500rpm and 540 at 5000 so you can see i have tq whereever i need it to be. My opinion is to go for it aslong as the block is good, im sure you will be quite pleased (especially stroked).


*EDIT and if you dont use the 427 you want to sell the alt bracket and power streeing bracket? haha i need badly

Last edited by Dmaleck; 01-24-2008 at 02:05 PM.
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Old 01-24-2008, 04:39 PM
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I think they are great motors I had two of them with twin turbos in a 28 ft. Donzi they were rated 425 hp @ 3800 and and as I recall 3psi boost ,I propped it to turn 44 to 4600 @ about 7psi ,aside from breaking one crank @ about 900 hrs I can't complain , and they all didn't have steel shafts !
And this was a factory install ,not custom builds .
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Old 01-24-2008, 05:59 PM
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I had one in my 57 Chevy,They will make a good motor with alot of torque!!!!At 50 mph I could light up the 18.50 tires with a 300 gear.
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Old 07-25-2012, 02:45 PM
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427 with longer rods and e85

i'm looking for a tall deck big block. i have a 9.8 standard deck but i want to build something different. a tall deck 427 with regular pistons and 6.535 rods. running e85 (12.5:1) and a 4 to 7 swap on the cam. and a big enough cam to get to at least 7500 rpms without hesitation. perhaps some steel merlin heads, yeah, the whole l88 thing with new components i suppose. yeah, everybody likes cubes over baby rats but i'm running a 55 gasser in the whole nostalgia scene. doug nash 5 speed running a ford straight axle, not a kit one either. doing it old school, somewhat limited budget by my own hand.
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Old 07-28-2012, 04:37 PM
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Can anything be done with the 366 tall decks or are they just scrap .
I have one and the crank I believe is the same as a 396 .
Maybe some one will need the crank and I can just toss the rest
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Old 07-28-2012, 07:39 PM
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curious if you could get by a run a 4.5" stroke crankshaft in a tall deck block with the extra meat?
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Old 07-29-2012, 12:19 AM
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nevermine my post above, found a few answers to that.. not a good idea anyway
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Old 07-29-2012, 07:24 AM
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The 366 and 427 tall deck motors were built for heavy duty applications. The 366 is basically useless in my opinion, and isn't really worth much. The 427 is a better choice, but with the aftermarket blocks available and the inherent issues with factory blocks, there really isn't any reason to use one in a performance build unless it's kept mild. Unless you're going to run monster cubes, there is no need for the extra deck height offered by the tall deck blocks. They used a 10.2" deck height over the standard 9.8" deck so they could run a taller 4 ring piston. This provided more stability in the bore, and the 4th ring provided better oil control on the bottom end. The specs for the 427 truck block are IDENTICAL in bore and stroke to the standard 427 with the expection of the block, and the tall deck is heavier as well. The crank and rods are also the same as a standard deck 427. On a production block, max safe overbore without filling is around .060", and you can stroke it about 1/4" max, but beware. Those engines are like their counterparts in that the main oil gallery runs along the left pan rail, and it's easily trashed by over clearancing for large strokes. Something else to consider is intakes and distributors. You'll need an intake made for tall deck applications, or spacers for a standard intake, and a distributor for a tall deck unless the intake has been milled for a standard one. I'd shy away from it as you're not gaining anything by running that block, as you can build the same combos with a standard deck, unless it's just something you want to do, but don't expect anything special from it. The blocks aren't any stronger than a standard block either, there is no "extra meat" in the castings other than the taller decks.

I'm not saying don't use it at all, but there are better choices for builds. Some might chime in and say they have over bored them .100", and there are pistons available, but that block better be filled at least to the bottom of the water pump holes, it's gonna weigh a ton more because of that, and the life of the block will be short.........not worth it in any case. And no, NO truck block from the 366/427 series in the Gen IV model has ever had siamesed cylinder bores. Bowtie blocks and aftermarket blocks generally do, and that's still the better choice. I'm not sure about the Gen VI motors, but the Gen V didn't either...........

Just had to edit this, seen something else to add. Yes, you can run longer rods when you use a tall deck, but what's the point? There is no advantage to running longer rods, and any gains you might see are so small that you'd never notice the difference. The whole "rod length to stroke ratio" thing has been blown all out of proportion. Strokers need shorter pistons, which allows for more piston rock. Longer rods moves the pin bore further up the piston which can increase piston rock, and depending on rod length, the pin bore can intersect the ring lands requiring a support rail. While this is fine for short duration racing engines, anything else it's a waste of money. In the words of "The Professor" Warren Johnson, "rods are to connect the pistons to the crank. build your short block, determine your piston needs, then put a rod in to connect them that fits........"

Last edited by predator carb guru; 07-29-2012 at 07:30 AM.
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